The present invention relates to a non-round container or article labeling machine and corresponding method. Labeling non-round articles in the past with wrap-around labels has been limited to turret-type labeling machines. This is because a turret-type machine has been the only method for consistently rotating an article as a label is being wrapped around it. Although attempts have been made to label non-round containers using very soft roll-on-pads in a compression roll-through labeling machine, none of these attempts have produced a commercially viable product. The reason for this is that even though a soft roll-on-pad can absorb the irregular surface of the container, the compression roll-through process fails to provide the torque necessary to consistently rotate the container throughout the entire labeling operation.
A compression roll-through labeling machine provides torque to rotate the article being labeled by friction of the rotating vacuum drum rolling the article against a stationary roll-on-pad. This friction is not just the friction of the vacuum drum against the article, but the friction of the vacuum drum against the label and the label against the article. With round articles, the required torque to induce rotation is constant throughout the labeling process, and this torque is easily obtained by pressing the container against the vacuum drum with the compression of the roll-on-pad. However, with non-round articles, the torque required for rotation varies greatly during the labeling process.
With a non-round article in a standard compression roll-through machine, the greatest amount of torque is required to rotate the article when a flat side is toward the vacuum drum. This is because of two reasons. The first is because a flat side causes the least amount of compression on the roll-on-pad, and any attempt to rotate the article from the flat side results in greater compression, hence greater required torque. The second reason is that as a non-round article rotates from a flat side to a corner, the center of mass has to quickly change its direction of movement, resulting in an inertial load that gets worse with speed.
The need for additional rotational torque is greatly compounded by the fact that the greatest torque is needed is when a compression roll-through machine delivers the least. This is due to the fact that the roll-on-pad pressure is minimal when the flat of an article is against the vacuum drum. Any attempt to increase the roll-on-pad pressure to give more torque also increases the required torque, and so stable rotation can never be achieved. Only articles with high coefficients of friction (to increase the torque) and almost-round profiles can be labeled with any degree of success in a standard compression roll-through labeling machine.
In view of the foregoing, it would be desirable to provide an improved labeling machine and corresponding method for applying labels to non-round containers or articles.